The disproportionation, to metathesis, of olefins is a reaction in which one or more olefinic compounds are transformed into other olefins of different molecular weights. The disproportionation of an olefin with itself to produce an olefin of a higher molecular weight and an olefin of a lower molecular weight can also be referred to as self-disproportionation. For example, propylene can be disproportionated to ethylene and cis-, and trans-2-butene. Another type of disproportionation involves the cross-disproportionation of two different olefins to form still other olefins. An example would be the reaction of one molecule of 2-butene with one molecule of 3-hexene to produce two molecules of 2-pentene.
By the term "disproportionation" or "metathesis" throughout this specification is meant the conversion of the feed olefinic (or unsaturated) hydrocarbon to a mixture of olefinic (or unsaturated) hydrocarbons having different numbers of carbon atoms than the feed hydrocarbons.
Many catalysts have been developed for olefin disproportionation. For example, those comprising inorganic oxide supports containing a catalytic amount of metal or metal oxide have been employed widely for conversion of olefins. While many such catalysts are known, it is a continuing objective of those of skill in the art to provide catalysts with improved productivity, i.e., increased conversion of starting material and/or improved selectivity to the desired product. The present invention is based upon the discovery of a way to dramatically improve the activity of certain disproportionation catalysts.